On Friday, January 24, 2020 at 8:45:53 PM UTC-7, Brent wrote: > > > > On 1/24/2020 6:58 PM, Alan Grayson wrote: > > > > On Friday, January 24, 2020 at 3:50:54 PM UTC-7, Brent wrote: >> >> >> >> On 1/24/2020 2:08 PM, John Clark wrote: >> >> On Fri, Jan 24, 2020 at 3:06 PM 'Brent Meeker' via Everything List < >> [email protected]> wrote: >> >> >>> >> If you're assuming that Real Numbers exist and that even a 1 cm >>>> universe would need a infinite number of labels >>> >>> >>> * > But not an infinite range of labels.* >>> >> >> OK now it's official, I have no idea what you're talking about. >> >> >> I ask my question again: >>>> *What is the difference between a "finite" universe that is expanding >>>> and accelerating and an infinite universe that is expanding and >>>> accelerating?* >>> >>> >>> * > Imagine the Earth is expanding like a balloon and at an accelerating >>> pace. * >>> >> >> A balloon is a terrible analogy for the Earth and a inflating balloon is >> an even worse analogy for a universe that will expand and accelerate >> forever. With the balloon you're standing outside of it watching the >> balloon expand into something that's already there, >> >> >> But you don't have to stand outside of it. Everything in the analogy is >> observable for a Flatland creature living on the sphere. >> >> but you can't stand outside of the universe and the universe is not >> expanding into anything that's already there. >> >> >>> *> You can't go fast enough to circumnavigate it because there's a speed >>> limit. * >>> >> >> And to call that speed limit the speed of light would be true but tends >> to trivialize it, really it's something far more fundamental and profound, >> it's the very speed of causality. >> >> >> So what. I'm making an analogy, not a model. >> >> >> >>> *> In your imagination is it finite or infinite? Are there locations on >>> it which are finite distances apart? Is there a set of such locations >>> connecting any two points? Is the sum of the distances between locations >>> of such a set finite?* >>> >> >> I would say a infinite amount of information would be needed to >> adequately >> >> >> Nobody asked about the amount of information. That's a red herring that >> LC threw in. The question was about the expansion and size of the universe. >> >> describe the evolution of the phase space (all possible values of the >> position and momentum of the particles in the universe) of such a expanding >> accelerating universe. It's infinite because no amount of approximation >> would be good enough for prediction, due to the accelerated creation of new >> space there will always be more values of position and momentum that >> particles can be in tomorrow than they can be in today. By the way, all >> this talk about the distance between particles in a expanding accelerating >> universe is rather ambiguous if you don't specify when, and "now" has no >> meaning everybody agrees with. >> >> And I've heard a bunch of bad analogies but I still haven't heard a >> direct answer to my question: >> What is the difference between a "finite" universe that is expanding >> >> >> As in my analogy, in a finite universe there are a finite number of >> intervals of finite distance that can link any two points in the universe. >> Of course this refers to it being finite at a given time, and you raised >> the problem of defining what counts as "at the same time". The answer is >> that it is at the same time if it is at the same degree of >> expansion...operationally it means that two distant events are "at the same >> time" if the isotropic temperature of the CMB looks the same to them. >> >> Brent >> > > > *You sometimes refer to the scale factor in GR being a function of time, > namely a(t). But in relativity each observer has a clock, and time is what > the observer reads on his clock. So what time are you referring to; the > clock of a bird's eye observer outside the universe? TIA, AG * > > > In the equation "t" is just a parameter. The physical clock is the > expansion itself, which is most conveniently measured by the CMB > temperature. >
OK, but then, as I suggested many moons ago, there IS such a thing as absolute motion, and it's with respect to the CMB. AG > But if you read Ned Wright's tutorial he points out that there are > different ways to assign a size to the observable universe because of the > frame dependence of simultaneity. > > Brent > > >> and accelerating forever and an infinite universe that is expanding and >> accelerating forever? >> >> John K Clark >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/everything-list/CAJPayv28VWSwcimZqwLvHfJkkUruOSi4%3DZKn8QtvYF4Un4t6og%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/everything-list/CAJPayv28VWSwcimZqwLvHfJkkUruOSi4%3DZKn8QtvYF4Un4t6og%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> >> -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/b1716c23-f8fc-4d26-86d9-5c8a47bb6300%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/b1716c23-f8fc-4d26-86d9-5c8a47bb6300%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/dbbb8b5d-c3c2-49fd-8ddf-5fe0b11c7b8d%40googlegroups.com.
